//1像素边框
border-1px($color)
  position: relative
  &:after
    content: ''
    position: absolute
    bottom: 0
    left: 0
    display: block
    width: 100%
    border-top: 1px solid $color
//关闭1像素边框
border-none()
  &:after
    display: none
/*2倍3倍图片*/
bg-image($url)
  background-image: url($url + "@2x.png")
  @media (-webkit-min-device-pixel-ratio: 3),(min-device-pixel-ratio: 3)
    backfround-image: url($url + "@2x.png")

